Visual Pathways of the Brain

In order for perception to occur, the physiological signal that starts in the retina must travel to the visual cortex. As we saw in the diagram of the retina, there are several layers of neurons which lead to the optic nerve. In the diagram of the brain we see that the optic nerve travels from the retina to the lateral geniculate nucleus (L.G.N.) in the mid brain. The neurons then become the visual radiations which travel to the visual cortex at the back of the brain. The visual cortex is also called the striate cortex and the occipital cortex.

You will notice that each retina is divided in two halves: the left and the right. The right visual field represented by the red bar at the top is projected to the left half of each retina. The reverse is true for the green bar. The left half of each retina is projected to the left half of the brain and the right half of each retina is projected to the right half of the brain.

This may seem strange considering that the left half of ones body is represented in the right brain and the right half of the body is represented in the left brain. But, we must remember that the retina really is part of the brain. So its representation in the higher centers makes sense.